This invention relates to jouunal gas bearings, and more particularly to a journal gas bearing body which is formed with a cylindrical bore to rotatably support therein a journal part of a shaft and gas introducing holes radially opening into the cylindrical bore.
In journal gas bearings which are employed, for example, in automotive turbochargers and also in instruments for measuring dynamic balance of turbochargers or the like, the journal part of a rotating shaft is floated on an annular film of a compressed gas which is introduced into the bearing through radial holes bored in the bearing body. Usually, opposite end sections of the cylindrical bore in the bearing body are used as true bearing sections. That is, in the respective end sections the clearance between the shaft and the cylindrical inner surface of the bearing body is strictly determined and in these sections the gas introducing holes open in the cylindrical inner surface.
However, in the bearing sections the rotating shaft comes into direct contact with the inner surface of the bearing body at starting and stopping operation and also when a large amount of unbalance arises in the rotation of the shaft. Therefore, it is necessary to afford wear resistance to the cylindrical inner surface of the bearing body in its bearing sections by making a hardening treatment such as a nitriding treatment or by using a ceramic or a cemented carbide in the bearing sections. However, when such a measure is taken and especially when a ceramic or cemented carbide is used difficulties are encounted in boring the gas introducing holes and in polishing the cylindrical inner surface in the bearing sections, so that great increase in the manufacturing cost of the bearing body is inevitable.